Azure SQL Managed Instance Business Critical tier is built for high performance databases and applications that require low IO latency of 1-2ms in average with up to 100K IOPS that can be achieved using fast local SSD that this tier uses to place database files.

Azure SQL Managed Instance Business Critical tier is a cluster of SQL server database engines with one primary read/write replica, one free-of-charge read-only replica, and two hidden replicas that ensure 99.99% availability.

High availability is implemented using SQL Server Always On technology that ensures that changes made on the primary server are replicated to at least two replicas before the transaction is committed. changes are synchronously written into the log files of secondary nodes.

With Business Critical General availability, we are also enabling a set of new features: